There are already known cushions comprising a filling of a foam-like mass of synthetic plastics material, said mass being adaptable to the shape of a part to be supported, in particular to a body portion to be supported. In a known cushion of this type the foamed material is arranged in a thin envelope of sheet material, for example a fabric, and consists of thermoplastic hollow microspheres which are mutually interconnected in a separable manner by means of a small amount of a pasty substance or of a substance in the form of a liquid at body temperature. The foamed material has a very low density of 0.02 to 0.3. Such known cushions are particularly suitable in the fields of application in which the shape adapted to the body portions remains unchanged also in future as is, for example, the case with ski boots which are always worn by the same person. If it is, however, required to adapt cushions having already a certain shape to another body portion, these cushions must, because they have no elastic properties with respect to tension forces, be brought into their original shape prior to adaptation to the other body portion.
There are also known cushions for shoes or boots and having a thixotropic mass or a mass of high viscosity, for example an oil having incorporated therein silicates or a liquid synthetic plastics material, filled into an envelope, for example a sheet of polyvinyl chloride. These cushions have plastic properties and are well capable of becoming shaped under pressure to shape of the parts to be supported but are heavy and have no elastic properties with respect to pressure and tension forces and thus lack the desired supporting comfort. Furthermore, the deformed cushions do not restore their original shape without the action of external forces and for changing their shape the action of an external force is required.
In another known cushion the filling consists of thermoplastic hollow microspheres which are mutually interconnected in an inseparable and elastic manner by means of a polysulfide or a polysiloxane. These cushions become adapted to a certain shape of the body only under a high dynamic pressure and can thus be used in an optimum manner only in such cases in which a high pressure acts on a small surface as is for example the case with orthopaedic supports or with crutches; the cushion and this remains elastic with respect to pressure forces after any adaptation.